Schedule II, Valuation and Qualifying Accounts (Details) - Allowance for Bad Debts - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Jan. 1		$ 5.6	$ 4.9	$ 4.9
Charged to costs and expenses		7.0	4.2	4.1
Charged to other accounts	[1]	2.1	1.0	0.9
Deductions from reserves	[2]	(9.2)	(4.5)	(5.0)
Balance at Dec. 31		$ 5.5	$ 5.6	$ 4.9

[1] Recovery of amounts previously written off.

[2] Deductions related primarily to bad debt write-offs.